What do i need to change as far as my speedo gear, when i change from an 2.73 to a 3.42 on an automatic tranny and electronic speedo. Will a sending unit from a manual tranny work on the automatic, and/or do i have to change the internal gear.

 

You need to change both the speedo gears to get it to read correctly. Right now you have a red 17 tooth gear on the trans output shaft. You need to change it to the gray 15 tooth gear, and you need to change the gear on your sending unit to the yellow 42 tooth gear. These are the gears I ran in mine when I changed from 2.73 to 3.42. Nothing from a manual trans will work. They're completely different in size. Most Chevy dealerships can still order the gears for you. That's where I bought mine from. Oh yeah, almost forgot, they'll usually say you need to buy a new sleeve with the new gear for the sending unit. You don't need a new sleeve. That's only for the cable driven speedos, and even on those, both sleeves are identical. So all you need to order is the two gears and you'll be set.

 

do they make speedo gears for a 3.45 gear 9 bolt or would that 3.42 speedo gear work fine with the 3.45?

 

Did u have to change anything else or will the 3:42's fit right in where the 2.73's were?

 

I would imagine that gear combo would be pretty accurate for 3.45's also. If not, all you'd have to do is increase the driven gear by one tooth more by using a 43 tooth driven gear instead of the 42 tooth.

 

No need to change anything else.